1. Field of the Invention
This invention relates to an electrical connector for circuit boards.
2. Description of the Related Art
electrical connectors for connecting the circuit on a circuit board with an external circuit are available in the art. One type of electrical connector for this purpose is fitted onto an edge portion of the circuit board to make contact with a connecting portion of the circuit.
An example of such an electrical connector is illustrated in FIG. 5. The connector includes an insulating housing 51 from which two parallel rows of contacts 52 extend in cantilevered fashion. A circuit-board receiving groove 54 is formed in a projecting portion 53 located at both ends of the housing 51, and a portion of the circuit board receiving groove 54 has a key portion 55. The two rows of parallel contacts 52, one located above the other, include intermediate portions bent in such a manner that the opposing contacts in the two rows approach each other leaving a space between them which is smaller than the thickness of a circuit board P.
The circuit board P has a row of connecting circuit portions P1 formed along one edge portion thereof. This edge portion is provided with guide grooves P3, one on each side of the row of connecting circuit portions Pl, which are guided by respective ones of the keys 55.
When the connector is to be connected, a cream solder is sufficiently applied over an area S of the circuit portions P1 of circuit board P, after which the circuit board P is inserted between the upper and lower rows of the contacts 52 in such a manner that the guide grooves P2 mate with the keys 55 of the connector. As a result, the upper and lower contacts 52 make contact with the corresponding circuit portions P1. This is followed by heating the circuit portions P1 so that each contact is soldered and connected to the circuit on the circuit board P.
The following problems arise in the electrical connector for circuit boards in the example of the prior art described above:
(1) From the moment the contacts 52 start to contact the edge portion of the circuit board until the moment the connector has been fitted on the circuit board at the correct position, the contacts are in a sliding state relative to the circuit portions P1. As a consequence of such sliding, the cream solder is removed from the vital portions at which the contacts 52 make contact with the circuit portions P1.
(2) If the contacts 52 abut against the circuit portions P1 with a high pressure while sliding against the circuit portions P1 as described above, the surface of the contact portions P1 is scraped off.
(3) In the process for fitting the connector onto the circuit board P, the pressure which one applies upon the other is constant and therefore it is not possible to tell when the connector has arrived at the correct fitting position. In addition, since there is an inclination between the two in the direction of connector width, there is no assurance that the fitting of the connector on the circuit board will be accomplished reliably.
(4) The connector and the circuit board rely upon the keys 55 and guide grooves P3 for a proper fit. In order to achieve reliable positioning, the keys 55 and guide grooves P3 must be machined to a high precision.